Guide vane ring for a turbomachine and turbomachine

ABSTRACT

The present invention relates to a guide vane ring ( 1 ) for a turbomachine, having a plurality of rotatable guide vanes ( 3 ), and having an inner ring ( 5 ), wherein the inner ring ( 5 ) has a seal ( 17 ) for sealing a radial gap between the inner ring ( 5 ) and an opposite-lying rotor segment ( 7 ), and wherein the inner ring ( 5 ) comprises at least two inner ring segments ( 11 ). The inner ring ( 5 ) is produced from a material or has a material that has a heat expansion coefficient α of less than 6*10 −6  per Kelvin in a temperature range between at least 20 degrees Celsius and 90 degrees Celsius. In addition, the present invention relates to a turbomachine having at least one guide vane ring ( 1 ) according to the invention.

BACKGROUND OF THE INVENTION

The studies that have led to this invention were supported according tothe Financial Aid Agreement No. CSJU-GAM-SAGE-2008-001 under the SeventhFramework Program of the European Union (FP7/2007-2013) for Clean SkyJoint Technology Initiative.

The present invention relates to a turbomachine and a guide vane ringfor a turbomachine.

Guide vane rings for turbomachines are subjected to intense temperaturefluctuations during operation. For example, when starting up an aircraftengine, temporarily high temperature gradients form in the inner ringsof guide vane rings, which can lead to deformations. These deformationsthat regress again in the further operation of the engine after thestartup procedure may influence secondary flows, such as, for example,leakage flows between inner rings on guide vanes and rotors. Theseinfluences reduce the overall efficiency of the engine.

SUMMARY OF THE INVENTION

An object of the present invention is to propose a guide vane ring for aturbomachine that reduces the leakage flow between a rotor segment andan inner ring. In addition, an object of the present invention is topropose a turbomachine with a guide vane ring according to theinvention.

The object according to the invention is achieved by a guide vane ring,which is discussed in detail below. It is further achieved by aturbomachine according to the present invention.

Thus, according to the invention, a guide vane ring for a turbomachine,in particular for a compressor, is proposed, which comprises a pluralityof rotatable guide vanes and an inner ring. The inner ring has a sealfor sealing a radial gap between the inner ring and an opposite-lyingrotor segment. The inner ring comprises at least two inner ringsegments.

The inner ring is produced from a material or has a material that has aheat expansion coefficient α of less than 6*10⁻⁶ per Kelvin in atemperature range between at least 20 degrees Celsius (° C.) and 90degrees Celsius (° C.). The lower and upper temperature values may vary,each time depending on the application of the guide vane ring accordingto the invention. For example, aircraft engines may have differenttemperatures in different operating states. The upper temperature valuecan be slightly or clearly greater than 90° C., for example 150° C.,300° C., 500° C., 800° C., or another value. For example, the lowertemperature value can be less than 20° C., for example 0° C., −10° C.,−20° C., or another value, each time depending on the location of anaircraft with an aircraft engine that has a guide vane ring according tothe invention.

The heat expansion coefficient α can be called a coefficient of linearthermal expansion. The value and the unit of the coefficient of thermallinear expansion α of 6*10⁻⁶ per Kelvin can be represented as 6*10⁻⁶/Kor as 6 ppm/K (ppm=parts per million).

The heat expansion coefficient α of the material of the inner ring canbe less than 6*10⁻⁶/K, for example, the heat expansion coefficient α canhave a value of 5*10⁻⁶/K, 2*10⁻⁶/K, 1.7*10⁻⁶/K, 1.2*10⁻⁶/K, 0.55*10⁻/K,or another value. An inner ring having these values for the heatexpansion coefficient α can advantageously have a linear expansion thatis reduced by approximately 60% to 65% in comparison to the usuallyemployed stainless iron-nickel-chromium alloys (the parts are indicatedin weight percent for these alloys in the overall discussion ofadvantages given below) with clearly higher values of the heat expansioncoefficient α (for example a heat expansion coefficient α of 15*10⁻⁶/K,20*10⁻⁶/K, 25*10⁻⁶/K, or 30*10⁻⁶/K). By means of this reduced linearexpansion, it can be achieved advantageously that, in particular, theend regions are deformed to a lesser extent in the peripheral directionof inner ring segments when compared to inner ring segments of theusually employed stainless iron-nickel-chromium alloys. This smallerdeformation of the inner ring segments can have the consequence thatsealing fins produce incisions that are less pronounced in inlet sealsat the radially inner ends of the guide vane ring, and thus leakageflows can be reduced in this region.

The guide vane ring according to the invention may have adjustable guidevanes and/or inlet seals. Upon first-time startup, sealing gaps can beforged or cut in between the inlet seals and sealing fins on radiallyopposite-lying rotors by means of these inlet seals. The sealing gaps,in which leakage flows usually form during operation of theturbomachine, can be reduced or minimized in this way.

Advantageous enhancements of the present invention are the subject ofeach of the dependent claims and embodiments.

Exemplary embodiments according to the invention may have one or more ofthe features named in the following.

In particular, gas turbines are described in the following asturbomachines purely by way of example. but without wanting to limitturbomachines to gas turbines. The turbomachine can be an axialturbomachine, in particular. The gas turbine can be an axial gasturbine, in particular, for example an aircraft gas turbine.

In specific embodiments according to the invention, the material of theinner ring has a heat conductivity λ of more than 10 watts per meter andper Kelvin (10 W/(m*K)) at a temperature between 20° C. and 25° C., inparticular at 23° C. The heat conductivity X may be, for example, 13W/(m*K), 15 W/(m*K), 30 W/(m*K), 50 W/(m*K), or another value.Advantageously, the heat from the inner ring segments can be rapidlyconducted further or discharged by means of a high heat conductivityvalue λ, and thus a local deformation of the material can be avoided. Inthis way, for example, the formation of a large sealing gap between asealing fin and an inlet seal can be reduced or avoided, andadvantageously a leakage flow is minimized.

In certain embodiments according to the invention, the inner ringcomprises at least two divided inner ring segments on the periphery ofthe inner ring. The ring segments can each have a peripheral angle of180 degrees (180°) as so-called half rings. The ring segments can alsohave other peripheral angles, for example, 120° and 240°. The inner ringmay have more than two ring segments, for example three ring segments,each having a 120° peripheral angle, four ring segments each having a90° peripheral angle, or other values.

In several embodiments according to the invention, the material of theinner ring is a nickel-alloyed steel. The nickel fraction in thematerial may comprise at least 25 weight percent.

In many embodiments according to the invention, the material of theinner ring has an iron fraction of at least 50 weight percent.

In specific embodiments according to the invention, the material of theinner ring has a cobalt fraction of at least 10 weight percent.

In several embodiments according to the invention, the material of theinner ring has an iron fraction between 62 weight percent and 66 weightpercent, in particular 64 weight percent, and a nickel fraction between34 weight percent and 38 weight percent, in particular 36 weightpercent.

In some embodiments according to the invention, the material of theinner ring has an iron fraction between 52 weight percent and 56 weightpercent, in particular 54 weight percent, a nickel fraction between 27weight percent and 31 weight percent, in particular 29 weight percent,and a cobalt fraction between 15 weight percent and 19 weight percent,in particular 17 weight percent.

Some or all embodiments according to the invention may have one,several, or all of the advantages named above and/or in the following.

By means of an inner ring according to the invention, designed inparticular as the inner ring of a compressor, which is produced from amaterial having an iron fraction of approximately 54 weight percent andhaving a nickel fraction of approximately 36 weight percent, in atemperature range between 20° C. and 500° C., a linear expansion reducedby approximately 60% to 65% can be achieved advantageously in comparisonto one of the following materials (the percentage data refer to weightpercents):

1) stainless steel (iron-nickel-chromium alloy) having the followingcomponents in weight percent: 0.03 to 0.08% carbon (C), less than orequal to 1% silicon (Si), 1 to 2% manganese (Mn), less than or equal to0.025% phosphorus (P), less than or equal to 0.015% sulfur (S), 13.5 to16% chromium, 1 to 1.5% molybdenum (Mo), 24 to 27% nickel (Ni), 0.1 to0.5% vanadium (V), 1.9 to 2.3% titanium (Ti), 0.003 to 0.01% boron (B),less than 0.35% aluminum (Al), with the remaining fraction: iron (Fe).

2) stainless steel (iron-nickel-chromium alloy) having the followingcomponents in weight percent: less than 0.08% carbon (C), less than0.35% silicon (Si), less than 0.35% manganese (Mn), less than 0.015%phosphorus (P), 0.2 to 0.8% aluminum (Al), less than 0.6% boron (B),less than 1% cobalt (Co), 17 to 21% chromium, less than 0.3% copper(Cu), 2.8 to 3.3% molybdenum (Mo), 4.75 to 5.5% niobium (Nb), 50 to 55%nickel (Ni), 0.65 to 1.15% titanium (Ti), with the remaining fraction:iron (Fe).

The thermal deformation can be considerably reduced by means of theinner ring according to the invention (see above). Thus, the rubbing ofsealing tips of the rotor into inlet seals of the inner ring can bereduced, in particular, in temporary (transient) operating states, suchas, for example, during the startup of an aircraft engine. This reducedrubbing-in advantageously can lead to a permanent reduction of leakageflows between the inner ring and the rotor.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be explained in the following by an examplebased on the appended drawings, in which identical reference numbersdesignate identical or similar components. In the schematicallysimplified figures:

FIG. 1 shows a guide vane ring according to the invention with arotatable guide vane, an inner ring, and a rotor segment;

FIG. 2 shows an inner ring segment in perspective representation; and

FIG. 3 shows a gas turbine with a guide vane ring according to theinvention in a schematically greatly simplified manner.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a guide vane ring 1 according to the invention, having arotatable guide vane 3, an inner ring 5, and a rotor segment 7. Theguide vane 3 is disposed rotatably in the inner ring 5 by means of aninner journal 9. The inner ring 5 comprises divided inner ring segments11 in the peripheral direction u.

The rotor segment 7 is joined to a rotating blade 13. Another upstreamrotor segment 15 is flanged to the rotor segment 7.

The inner ring segments 11 are joined to seals, in particular to inletseals 17, at their radially inner ends. A leakage flow 21 can formduring the operation of the turbomachine between the inlet seals 17 andsealing tips or sealing fins 19, which, in particular, are joinedintegrally to rotor segment 7. The leakage flow 2 usually runs counterto the primary flow direction 23 of the turbomachine (dependent on thepressure ratios upstream and downstream of the guide vane ring 1).

In turbomachines, in particular in compressors of aircraft engines, therotor segments 7 and 15, the sealing fins 19, the inner ring segments11, the rotating blades 13, as well as the guide vane ring 1 are oftensubjected to high temperature fluctuations approximately between 20° C.and 500° C. Both the lower temperature range as well as the uppertemperature range can be shifted still further, each time depending onthe application and the operating conditions. The named components canexpand, bend, or change their shape in another way, each time dependingon the materials employed. In particular, the linear thermal expansionof the inner ring segments 11 can influence the gap width between theinlet seals 17 and the sealing fins 19 and thus change the leakage flow21.

The inner ring 5 can be divided or segmented in the axial direction aand/or in the radial direction r and/or in the peripheral direction u(as inner ring segments 11 in FIG. 1). For reasons of assembly, theinner ring 5 is often designed in the shape of two half-ring segments,each of which may have a peripheral angle of 180 degrees. The inner ring5 can also be segmented differently in other embodiments, for exampleinto three segments, each with a 120 degree peripheral angle, into foursegments, each with a 90 degree peripheral angle, etc.

In one possible embodiment of a turbomachine as an aircraft engine, aradial temperature gradient can build up temporarily in the inner ringsegments 11, in particular upon startup of the engine. The inner ringsegments 11 then have a higher temperature radially outside (on theouter radius) than radially inside (on the inner radius). Based on thistemperature gradient, the ends of the inner ring segments 11 can bendradially inward temporarily (during the engine startup process),considered in the peripheral direction. Based on this temporary bendingof the inner ring 5, an increased rubbing of the sealing fins 19 intothe inlet seals 17 can result. After the inner ring 5 has completelyheated throughout (after the engine startup procedure), the temperaturegradient of the inner ring segments 11 can be reduced again in theradial direction r, and the deformation can regress again, for example,approximately back to the initial state. The gap which is formed betweenthe sealing fins 19 and the inlet seal 17 due to the temporarydeformation remains or exists, however, after the regression of theinner ring 5. This gap can effect or generate an elevated, possiblypermanent leakage flow 21. The efficiency of the engine can bepermanently reduced in this way.

The described effect of the temporary deformation of the inner ring 5based on temperature gradients can be designated as the so-called“cording effect” or “cording”. The “cording effect” is a thermal effectprimarily in the case of inner rings 5, which can lead to athree-dimensional deformation of the inner ring segments 11 at thedividing planes (in the peripheral direction u). These deformations canlead to a greater run-in of sealing fins 19 into the inlet seals 17,whereby the sealing gaps and leakages can increase. Greater leakages canreduce the efficiency.

The run-in (elevated rubbing of the sealing fins 19 into the inlet seals17) on the inner rings 5 can be advantageously reduced by means of theguide vane ring 1 according to the invention with the materialproperties named in the claims. Possible leakage losses due to elevatedleakage flows 21 can at least be reduced advantageously.

FIG. 2 shows an inner ring segment 11 with a separating plane 25 inperspective representation. The inner journals 9 of the adjustable guidevanes 3 are inserted into the depressions 27 on the radial outer side ofthe inner ring segment 11.

FIG. 3 shows in schematically very simplified manner a gas turbine 29 asan embodiment of a turbomachine according to the invention with a guidevane ring 1 according to the invention, which is disposed, for example,in the high-pressure compressor section of a gas turbine 29.

What is claimed is:
 1. A guide vane ring (1) for a turbomachine, havinga plurality of rotatable guide vanes (3), and having an inner ring (5),wherein the inner ring (5) has a seal (17) for sealing a radial gapbetween the inner ring (5) and an opposite-lying rotor segment (7), andwherein the inner ring (5) comprises at least two inner ring segments(11), wherein the inner ring (5) is produced from a material or has amaterial that has a heat expansion coefficient α of less than 6*10⁻⁶ perKelvin in a temperature range between at least 20 degrees Celsius and 90degrees Celsius.
 2. The guide vane ring (1) according to claim 1,wherein the material of the inner ring (5) has a heat conductivity λ ofgreater than 10 watts per meter and per Kelvin at a temperature between20 degrees Celsius and 25 degrees Celsius.
 3. The guide vane ring (1)according to claim 1, wherein the inner ring (5) comprises at least twodivided inner ring segments (11) on the periphery of the inner ring (5).4. The guide vane ring (1) according to claim 1, wherein the material ofthe inner ring (5) is a nickel-alloyed steel.
 5. The guide vane ring (1)according to claim 1, wherein the material of the inner ring (5)comprises a nickel fraction of at least 25 weight percent.
 6. The guidevane ring (1) according to claim 1, wherein the material of the innerring (5) comprises an iron fraction of at least 50 weight percent. 7.The guide vane ring (1) according to claim 1, wherein the material ofthe inner ring (5) comprises a cobalt fraction of at least 10 weightpercent.
 8. The guide vane ring (1) according to claim 1, wherein thematerial of the inner ring (5) has a heat expansion coefficient α ofless than 6*10⁻⁶ per Kelvin in a temperature range between at least 20degrees Celsius and 500 degrees Celsius.
 9. The guide vane ring (1)according to claim 1, wherein the guide vane ring (1) is configured andarranged in a turbomachine.
 10. The guide vane ring (1) according toclaim 9, wherein the turbomachine is an axial high-pressure compressor.